Hydraulic tappet



. May 14, 1957 A. B. HUBBARD ETAL HYDRAULIC TAPPET 2 sheds-sheet 1 y Filed Jan. 26, 1952 9W MM May 14 1957 A. B. HUBBARD ET AL. 2,791,993

vHYDRAULIC TAPPET Filed Jan. 26. 1952 2 vSheets-Shea?, 2

ber 18 at all times delivers oil to the annular recess 62 even though the tappet lbody or cylinder member 50 is moving up and down. The oil is delivered to the inside of the cylinder member 50 through la passage 66 disposed in the cylinder member at the lower end of the annular recess 62 as more clearly shown in Figs. l and 2.

The tappet 22 is also provided with a piston member 68, the upper end of which is provided with a recess 70 which receives the lower end of the push rod 32. The piston 63 is provided with a relatively large diameter-ed portion 72 which is slidably received within the relatively large diametered bore 54 in the upper end of the cylinder member 50. The lower end of the piston 63 is provided with a relatively small diametered section 74 which is slidably received within the relatively small diametered bore 56 of the cylinder member 50. The sections 72 and 74 are connected by a surface 76 which overlies the shoulder 58 formed between the bores 54 and 56 thereby forming a pocket between the piston 68 and the cylinder member 50.

The lower end of the piston 68 which is disposed within the cylinder member Sil is provided with an axially extending passage 78 which communicates with a radially extending passage 80, the latter terminating on the surface of the smaller diametered portion 74 which is immediately below the surface '76. The purpose of the passages 7S and 80 is to accommodate the ow of lubricant from the interior of the cylinder member t? to the pocket formed between the shoulder 56 and the surface 76.

In operation, when the closed end S2 of the tappet is riding on the heel of the cam 24, oil is pumped from the chamber 18 through the passage 64 into the annular recess 62 and from this recess through the passage 66 into the interior of the cylinder member 50 below the piston 68. The oil is also forced through the passages 78 and di) to the pocket disposed between the surface 76 of the piston 68 and the shoulder 5S of the cylinder member 59. The relatively large diametered portion 72 of the piston 63 is made to accommodate a slight clearance between its outer surface and the large diametered bore 54 located at the open end of the cylinder member 50. As a result the oil which is pumped to the pocket formed between the surface 76 and the shoulder 78 may leak upwardly and outwardly of the tappet between the large diametered portion 72 of the bore 54, the space 84 disposed in the cylinder block above the tappet being in direct communication with the oil sump of the internal combustion engine.

As more clearly seen in Fig. 2, when the closed end 52 of the cylinder member 50 rides up on the toe of the cam 24 during normal operation of the engine, the piston 68 and the cylinder member 50 are necessarily telescoped a small amount toward each other. At this movement the passage 80 is cut ofr from communication with the pocket formed between the surface 76 and the shoulder 5S by the upper extremity of the relatively small bore 56 of the cylinder member 5) and the surface 76 approaches the shoulder 5S effecting a dash-pot action herebetween. The excess oil is bled off through the small space between the walls of the bore 54 and the section 72. When this action occurs, a small amount of oil is trapped in the pocket formed by the surface 76 and the shoulder 58 thereby forming a cushioning layer of oil therebetween. This cushioning layer of oil prevents the lower edge of the section 72 of the piston 68 from sharply striking the shoulder 5S during normal relative oscillatory movement between the piston 68 and the tappet body 50. By preventing the striking blows of these parts, the noise which normally accompanies conventional hydraulic tappets is eliminated.

ln Figs. 4 and 5 we have shown a modification of the form of the invention shown in Figs. l, 2 and 3 and like numerals have been applied to like parts. In this form of the invention, a coil spring 90 has one end seated within the bore 60 of the cylinder member 50 and has its other end engaging the bottom of the piston 68. The spring 9i) is under compression and acts to urge the piston 68 out of the cylinder member 5G. The annular recess 62 in this form of the invention is narrower than its counterpart 62 shown in the form in Figs. l to 3 for the purpose of eliminating the *dow of pressure lubricant from the chamber 18 to the cylindrical member when the tappet rests on the heel of the cam 24. When the tappet is on the heel of the cam, pressure lubricant is not needed to maintain the piston under pressure since this action is accomplished by the coil spring 96. When, however, as viewed in Fig. 5, the tappet is engaged by the toe of the cam 24 and the oil cushion is needed between the surface 76 and the shoulder 58, the annular recess 62 comes into registration with the passage 64 to thereby eilect the circulation of the pressure lubricant or oil in the same manner as set forth relative to Figs. l to 3.

In Figs. 7 and 8, we have shown another modification of our invention. The numeral 120 represents a tappet bore disposed in the cylinder block generally designated by the numeral 110. A hydraulic tappet generally indicated by the numeral 122 is slidably disposed within the tappet bore 120 and is engaged at its lower end by a cam 124 which is formed as an integral part of a camshaft 126. The hydraulic tappet 122 includes a tappet body or cylinder member 15G provided with a uniformly diametercd bore 154 which extends from the open end of the cylinder member 150 to the closed end 152 of tively movable parts.

the cylinder member, the latter engaging the cam 124. The bore 154 slidably receives a piston 163 which has a first cylindrical section 174 disposed within the bore 154 and which has a diameter only slightly less than the diameter of the bore 154. The piston 122 is also provided with a second section 172 which is integrally connected to the first section by a neck portion 173. The second section 172 is of a cylindrical configuration and has an external diameter greater than the diameter of the bore 154 but smaller than the diameter of the tappet bore 120. The upper end face of the cylindrical member presents a shoulder 15S which in cooperation with the underside of the second section 172 forms parallel surfaces for accommodating an oil cushion between the piston 168 and the tappet body or cylindrical member 156. The tappet body or cylindrical member 15G is provided with an annular recess 162 which communicates with the chamber 18 through the passage 64 to thereby accommodate flow of pressure lubricant to the recess 162. The passage 166 is provided in the side of the cylindrical member at the lower end of the annular recess 162 to facilitate the reception of oil into the bore 154. The pressure lubricant or oil continually urges the piston 16S out of the cylindrical member 150 and escapes from the cylindrical member 150 by seeping between the surface of the rst section 168 of the piston and the surface of the bore 154 thereby causing a flow of pressure lubricant or oil between the shoulder 158 and the underside of the second section 162 to thereby effect an oil cushion at this location.

It will be seen in Figs. 7 and 8 that the passage 64 is in constant communication with the recess 162 thereby continually furnishing pressure uid to the interior of the tappet body 150. This lubricant or oil urges the piston 122 out of the bore 154 and maintains a tight operative connection between the cam 24 and the push rod 32. The oil supplied to the tappet body 150 under pressure continually escapes between the section 174 and the bore 154 and flows over the shoulder 158. When the tappet rides up to the toe of the cam 124, the under side of the piston section 172 approaches the shoulder 158 and is cushioned by the ever present layer of oil which continually ows over this shoulder.

The oil cushion provided in all forms of the invention shown herein prevents noisy operation of the tappets since the oil provides a dash-pot action between the rela- It should also be noted that in two forms of the invention only two parts form the cornplete hydraulic tappet. This number of parts is relatively few compared with conventional hydraulic tappets known in the art.

While we have illustrated and described but three ernbodiments of our invention, it is to be understood that such is for the purpose of illustration only, and yit is contemplated that those skilled in the art may modify certain details without departing from the spirit or scope of the invention as dened in the claims appended hereto.

We claim:

1. A valve lifting tappet including a cam engaging member comprising a cylinder having an inlet adapted for communicative connection with the pressure lubricating system of an internal combustion engine, said cylinder having a closed extremity at one end and a piston bore at its opposite end portion provided with an entrance surrounded by a shoulder portion extending transversely of said bore, and a piston member having a portion slidably mounted in said bore below said shoulder portion and adapted to be urged away from the closed end of said cylinder by the iluid pressure of said lubricating system, said piston member having a shoulder portion overlying said shoulder portion of said cylinder member in axially spaced relationship for accommodating the reception of a cushioning layer of lubricant between said shoulder portions and said piston being provided with a passage for accommodating the flow of lubricant from within said cylinder to the space between said shoulders.

2. A valve lifting tappet including a cam engaging member comprising a cylinder having an inlet adapted for communicative connection with the pressure lubricating system of an internal combustion engine, said cylinder having a closed extremity at one end and a relatively large diametered bore extending from the other end of said cylinder inwardly and terminating at a shoulder, said cylinder having a relatively small diametered bore extending inwardly of said cylinder from said shoulder, and a piston slidably disposed within said cylinder having relatively small and large diametered sections with a shoulder deposed therebetween, said small and large sections of said piston being disposed in a telescoping relationship with said small and large bores of said cylinder, respectively, said small section being provided with a passage for accommodating the ow of lubricant from within said cylinder to said shoulders to thereby form a cushioning layer of lubricant between said shoulders.

3. A valve lifting tappet including a cam engaging member comprising a cylinder having an inlet adapted for communicative connection with the pressure lubricating system of an internal combustion engine, said cylinder having a closed extremity at one end and a relatively large diametered bore extending from the other end of said cylinder inwardly and terminating at a shoulder, said cylinder having a relatively small diametered bore extending inwardly of said cylinder from said shoulder, and a piston slidably disposed within said cylinder having relatively small and large diametered sections with a shoulder deposed therebetween, said small and large sections of said piston being disposed in a telescoping relationship with said small and large bores of said cylinder, respectively, the small section of said piston being provided with a passage which extends from the end of said piston disposed within said cylinder to a location directly adjacent the juncture of said small section and said shoulder disposed between said sections, for accommodating the lovv of lubricant from within said cylinder to said shoulders to thereby form a cushioning layer of lubricant between said shoulders.

4. A valve lifting tappet including a cam engaging member comprising a cylinder having an inlet adapted for communicative connection with the pressure lubricating system of an internal combustion engine, said cylinder having a closed extremity at one end and a relatively large diametered bore extending from the other end of said cylinder inwardly and terminating at a shoulder, said cylinder having a relatively small diametered bore extending inwardly of said cylinder from said shoulder, and a piston slidably disposed within said cylinder having relatively small and large diametered sections with a shoulder deposed therebetween, said small and large sections of said piston being disposed in a telescoping relationship with said small and large bores of said cylinder, respectively, the small section of said piston being provided with a passage which extends from the end of said piston disposed within said cylinder to a location directly adjacent the juncture of said small section and said shoulder disposed between said sections, for accommodating the flow of lubricant from within said cylinder to said shoulders to thereby form a cushioning layer of lubricant between said shoulders the diameter of the large diametered section of said piston being predetermined relative to the diameter of the large diametered bore of said cylinder to accommodate leakage of said lubricant out of said cylinder.

References Cited in the le of this patent UNITED STATES PATENTS 1,583,335 Borschel May 4, 1926 1,718,589 Short June 25, 1929 1,751,716 Porth Mar. 25, 1930 1,784,767 Summers Dec. 9, 1930 1,798,938 Hallett Mar. 31, 1931 1,815,868 Schenk July 21, 1931 FOREIGN PATENTS 920,444 France Apr. 8, 1947 

